[PATCH 0/2] <asm/atomic.h> adjustments

[PATCH 0/2] <asm/atomic.h> adjustments

[Corneliu ZUZU]

Corneliu ZUZU (2):
  asm/atomic.h: common prototyping (add xen/atomic.h)
  fix: make atomic_read() param const

 xen/include/asm-arm/arm32/atomic.h |  11 ---
 xen/include/asm-arm/arm64/atomic.h |  11 ---
 xen/include/asm-arm/atomic.h       |  91 +++++++++++++++++++---
 xen/include/asm-x86/atomic.h       |  51 +++++-------
 xen/include/xen/atomic.h           | 155 +++++++++++++++++++++++++++++++++++++
 5 files changed, 257 insertions(+), 62 deletions(-)
 create mode 100644 xen/include/xen/atomic.h

-- 
2.5.0


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[PATCH 1/2] asm/atomic.h: common prototyping (add xen/atomic.h)

[Corneliu ZUZU]

Following Andrew Cooper's suggestion, create a common-side <xen/atomic.h> to
establish, among others, prototypes of atomic functions called from common-code.
Done to avoid introducing inconsistencies between arch-side <asm/atomic.h>
headers when we make subtle changes to one of them.

Some arm-side macros had to be turned into inline functions in the process.

Also includes a minor adjustment asm-x86/atomic.h: reorder atomic_inc_and_test()
to follow after atomic_inc().

Signed-off-by: Corneliu ZUZU <czuzu@bitdefender.com>
---
 xen/include/asm-arm/arm32/atomic.h |  11 ---
 xen/include/asm-arm/arm64/atomic.h |  11 ---
 xen/include/asm-arm/atomic.h       |  89 ++++++++++++++++++---
 xen/include/asm-x86/atomic.h       |  49 +++++-------
 xen/include/xen/atomic.h           | 155 +++++++++++++++++++++++++++++++++++++
 5 files changed, 255 insertions(+), 60 deletions(-)
 create mode 100644 xen/include/xen/atomic.h

diff --git a/xen/include/asm-arm/arm32/atomic.h b/xen/include/asm-arm/arm32/atomic.h
index 7ec712f..be08ff1 100644
--- a/xen/include/asm-arm/arm32/atomic.h
+++ b/xen/include/asm-arm/arm32/atomic.h
@@ -149,17 +149,6 @@ static inline int __atomic_add_unless(atomic_t *v, int a, int u)
 
 #define atomic_xchg(v, new) (xchg(&((v)->counter), new))
 
-#define atomic_inc(v)		atomic_add(1, v)
-#define atomic_dec(v)		atomic_sub(1, v)
-
-#define atomic_inc_and_test(v)	(atomic_add_return(1, v) == 0)
-#define atomic_dec_and_test(v)	(atomic_sub_return(1, v) == 0)
-#define atomic_inc_return(v)    (atomic_add_return(1, v))
-#define atomic_dec_return(v)    (atomic_sub_return(1, v))
-#define atomic_sub_and_test(i, v) (atomic_sub_return(i, v) == 0)
-
-#define atomic_add_negative(i,v) (atomic_add_return(i, v) < 0)
-
 #endif /* __ARCH_ARM_ARM32_ATOMIC__ */
 /*
  * Local variables:
diff --git a/xen/include/asm-arm/arm64/atomic.h b/xen/include/asm-arm/arm64/atomic.h
index b49219e..80d07bf 100644
--- a/xen/include/asm-arm/arm64/atomic.h
+++ b/xen/include/asm-arm/arm64/atomic.h
@@ -125,17 +125,6 @@ static inline int __atomic_add_unless(atomic_t *v, int a, int u)
 	return c;
 }
 
-#define atomic_inc(v)		atomic_add(1, v)
-#define atomic_dec(v)		atomic_sub(1, v)
-
-#define atomic_inc_and_test(v)	(atomic_add_return(1, v) == 0)
-#define atomic_dec_and_test(v)	(atomic_sub_return(1, v) == 0)
-#define atomic_inc_return(v)    (atomic_add_return(1, v))
-#define atomic_dec_return(v)    (atomic_sub_return(1, v))
-#define atomic_sub_and_test(i, v) (atomic_sub_return(i, v) == 0)
-
-#define atomic_add_negative(i,v) (atomic_add_return(i, v) < 0)
-
 #endif
 /*
  * Local variables:
diff --git a/xen/include/asm-arm/atomic.h b/xen/include/asm-arm/atomic.h
index 29ab265..8e8c5d1 100644
--- a/xen/include/asm-arm/atomic.h
+++ b/xen/include/asm-arm/atomic.h
@@ -2,6 +2,7 @@
 #define __ARCH_ARM_ATOMIC__
 
 #include <xen/config.h>
+#include <xen/atomic.h>
 #include <xen/prefetch.h>
 #include <asm/system.h>
 
@@ -95,15 +96,6 @@ void __bad_atomic_size(void);
     default: __bad_atomic_size(); break;                                \
     }                                                                   \
 })
-    
-/*
- * NB. I've pushed the volatile qualifier into the operations. This allows
- * fast accessors such as _atomic_read() and _atomic_set() which don't give
- * the compiler a fit.
- */
-typedef struct { int counter; } atomic_t;
-
-#define ATOMIC_INIT(i) { (i) }
 
 /*
  * On ARM, ordinary assignment (str instruction) doesn't clear the local
@@ -138,6 +130,85 @@ static inline void _atomic_set(atomic_t *v, int i)
 # error "unknown ARM variant"
 #endif
 
+#define atomic_inc_return(v)    (atomic_add_return(1, v))
+#define atomic_dec_return(v)    (atomic_sub_return(1, v))
+
+/**
+ * atomic_sub_and_test - subtract value from variable and test result
+ * @i: integer value to subtract
+ * @v: pointer of type atomic_t
+ *
+ * Atomically subtracts @i from @v and returns
+ * true if the result is zero, or false for all
+ * other cases.
+ */
+static inline int atomic_sub_and_test(int i, atomic_t *v)
+{
+    return 0 == atomic_sub_return(i, v);
+}
+
+/**
+ * atomic_inc - increment atomic variable
+ * @v: pointer of type atomic_t
+ *
+ * Atomically increments @v by 1.
+ */
+static inline void atomic_inc(atomic_t *v)
+{
+    atomic_add(1, v);
+}
+
+/**
+ * atomic_inc_and_test - increment and test
+ * @v: pointer of type atomic_t
+ *
+ * Atomically increments @v by 1
+ * and returns true if the result is zero, or false for all
+ * other cases.
+ */
+static inline int atomic_inc_and_test(atomic_t *v)
+{
+    return 0 == atomic_add_return(1, v);
+}
+
+/**
+ * atomic_dec - decrement atomic variable
+ * @v: pointer of type atomic_t
+ *
+ * Atomically decrements @v by 1.
+ */
+static inline void atomic_dec(atomic_t *v)
+{
+    atomic_sub(1, v);
+}
+
+/**
+ * atomic_dec_and_test - decrement and test
+ * @v: pointer of type atomic_t
+ *
+ * Atomically decrements @v by 1 and
+ * returns true if the result is 0, or false for all other
+ * cases.
+ */
+static inline int atomic_dec_and_test(atomic_t *v)
+{
+    return 0 == atomic_sub_return(1, v);
+}
+
+/**
+ * atomic_add_negative - add and test if negative
+ * @v: pointer of type atomic_t
+ * @i: integer value to add
+ *
+ * Atomically adds @i to @v and returns true
+ * if the result is negative, or false when
+ * result is greater than or equal to zero.
+ */
+static inline int atomic_add_negative(int i, atomic_t *v)
+{
+    return atomic_add_return(i, v) < 0;
+}
+
 #endif /* __ARCH_ARM_ATOMIC__ */
 /*
  * Local variables:
diff --git a/xen/include/asm-x86/atomic.h b/xen/include/asm-x86/atomic.h
index d246b70..9bf4bc1 100644
--- a/xen/include/asm-x86/atomic.h
+++ b/xen/include/asm-x86/atomic.h
@@ -2,6 +2,7 @@
 #define __ARCH_X86_ATOMIC__
 
 #include <xen/config.h>
+#include <xen/atomic.h>
 #include <asm/system.h>
 
 #define build_read_atomic(name, size, type, reg, barrier) \
@@ -79,15 +80,6 @@ void __bad_atomic_size(void);
     }                                                     \
 })
 
-/*
- * NB. I've pushed the volatile qualifier into the operations. This allows
- * fast accessors such as _atomic_read() and _atomic_set() which don't give
- * the compiler a fit.
- */
-typedef struct { int counter; } atomic_t;
-
-#define ATOMIC_INIT(i) { (i) }
-
 /**
  * atomic_read - read atomic variable
  * @v: pointer of type atomic_t
@@ -110,7 +102,6 @@ static inline int _atomic_read(atomic_t v)
     return v.counter;
 }
 
-
 /**
  * atomic_set - set atomic variable
  * @v: pointer of type atomic_t
@@ -217,6 +208,25 @@ static inline void atomic_inc(atomic_t *v)
 }
 
 /**
+ * atomic_inc_and_test - increment and test
+ * @v: pointer of type atomic_t
+ *
+ * Atomically increments @v by 1
+ * and returns true if the result is zero, or false for all
+ * other cases.
+ */
+static inline int atomic_inc_and_test(atomic_t *v)
+{
+    unsigned char c;
+
+    asm volatile (
+        "lock; incl %0; sete %1"
+        : "=m" (*(volatile int *)&v->counter), "=qm" (c)
+        : "m" (*(volatile int *)&v->counter) : "memory" );
+    return c != 0;
+}
+
+/**
  * atomic_dec - decrement atomic variable
  * @v: pointer of type atomic_t
  * 
@@ -250,25 +260,6 @@ static inline int atomic_dec_and_test(atomic_t *v)
 }
 
 /**
- * atomic_inc_and_test - increment and test 
- * @v: pointer of type atomic_t
- * 
- * Atomically increments @v by 1
- * and returns true if the result is zero, or false for all
- * other cases.
- */ 
-static inline int atomic_inc_and_test(atomic_t *v)
-{
-    unsigned char c;
-
-    asm volatile (
-        "lock; incl %0; sete %1"
-        : "=m" (*(volatile int *)&v->counter), "=qm" (c)
-        : "m" (*(volatile int *)&v->counter) : "memory" );
-    return c != 0;
-}
-
-/**
  * atomic_add_negative - add and test if negative
  * @v: pointer of type atomic_t
  * @i: integer value to add
diff --git a/xen/include/xen/atomic.h b/xen/include/xen/atomic.h
new file mode 100644
index 0000000..5d5c051
--- /dev/null
+++ b/xen/include/xen/atomic.h
@@ -0,0 +1,155 @@
+/*
+ * include/xen/atomic.h
+ *
+ * Common atomic operations entities (atomic_t, function prototypes).
+ * Include _from_ arch-side <asm/atomic.h>.
+ *
+ * Copyright (c) 2016 Bitdefender S.R.L.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __XEN_ATOMIC_H__
+#define __XEN_ATOMIC_H__
+
+/*
+ * NB. I've pushed the volatile qualifier into the operations. This allows
+ * fast accessors such as _atomic_read() and _atomic_set() which don't give
+ * the compiler a fit.
+ */
+typedef struct { int counter; } atomic_t;
+
+#define ATOMIC_INIT(i) { (i) }
+
+/**
+ * atomic_read - read atomic variable
+ * @v: pointer of type atomic_t
+ *
+ * Atomically reads the value of @v.
+ */
+static inline int atomic_read(atomic_t *v);
+
+/**
+ * _atomic_read - read atomic variable non-atomically
+ * @v atomic_t
+ *
+ * Non-atomically reads the value of @v
+ */
+static inline int _atomic_read(atomic_t v);
+
+/**
+ * atomic_set - set atomic variable
+ * @v: pointer of type atomic_t
+ * @i: required value
+ *
+ * Atomically sets the value of @v to @i.
+ */
+static inline void atomic_set(atomic_t *v, int i);
+
+/**
+ * _atomic_set - set atomic variable non-atomically
+ * @v: pointer of type atomic_t
+ * @i: required value
+ *
+ * Non-atomically sets the value of @v to @i.
+ */
+static inline void _atomic_set(atomic_t *v, int i);
+
+static inline int atomic_cmpxchg(atomic_t *v, int old, int new);
+
+/**
+ * atomic_add - add integer to atomic variable
+ * @i: integer value to add
+ * @v: pointer of type atomic_t
+ *
+ * Atomically adds @i to @v.
+ */
+static inline void atomic_add(int i, atomic_t *v);
+
+/**
+ * atomic_add_return - add integer and return
+ * @i: integer value to add
+ * @v: pointer of type atomic_t
+ *
+ * Atomically adds @i to @v and returns @i + @v
+ */
+static inline int atomic_add_return(int i, atomic_t *v);
+
+/**
+ * atomic_sub - subtract the atomic variable
+ * @i: integer value to subtract
+ * @v: pointer of type atomic_t
+ *
+ * Atomically subtracts @i from @v.
+ */
+static inline void atomic_sub(int i, atomic_t *v);
+
+/**
+ * atomic_sub_and_test - subtract value from variable and test result
+ * @i: integer value to subtract
+ * @v: pointer of type atomic_t
+ *
+ * Atomically subtracts @i from @v and returns
+ * true if the result is zero, or false for all
+ * other cases.
+ */
+static inline int atomic_sub_and_test(int i, atomic_t *v);
+
+/**
+ * atomic_inc - increment atomic variable
+ * @v: pointer of type atomic_t
+ *
+ * Atomically increments @v by 1.
+ */
+static inline void atomic_inc(atomic_t *v);
+
+/**
+ * atomic_inc_and_test - increment and test
+ * @v: pointer of type atomic_t
+ *
+ * Atomically increments @v by 1
+ * and returns true if the result is zero, or false for all
+ * other cases.
+ */
+static inline int atomic_inc_and_test(atomic_t *v);
+
+/**
+ * atomic_dec - decrement atomic variable
+ * @v: pointer of type atomic_t
+ *
+ * Atomically decrements @v by 1.
+ */
+static inline void atomic_dec(atomic_t *v);
+
+/**
+ * atomic_dec_and_test - decrement and test
+ * @v: pointer of type atomic_t
+ *
+ * Atomically decrements @v by 1 and
+ * returns true if the result is 0, or false for all other
+ * cases.
+ */
+static inline int atomic_dec_and_test(atomic_t *v);
+
+/**
+ * atomic_add_negative - add and test if negative
+ * @v: pointer of type atomic_t
+ * @i: integer value to add
+ *
+ * Atomically adds @i to @v and returns true
+ * if the result is negative, or false when
+ * result is greater than or equal to zero.
+ */
+static inline int atomic_add_negative(int i, atomic_t *v);
+
+#endif /* __XEN_ATOMIC_H__ */
-- 
2.5.0


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[PATCH 2/2] fix: make atomic_read() param const

[Corneliu ZUZU]

This wouldn't let me make a param of a function that used atomic_read() const.

Signed-off-by: Corneliu ZUZU <czuzu@bitdefender.com>
---
 xen/include/asm-arm/atomic.h | 2 +-
 xen/include/asm-x86/atomic.h | 2 +-
 xen/include/xen/atomic.h     | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/xen/include/asm-arm/atomic.h b/xen/include/asm-arm/atomic.h
index 8e8c5d1..cd86cf0 100644
--- a/xen/include/asm-arm/atomic.h
+++ b/xen/include/asm-arm/atomic.h
@@ -102,7 +102,7 @@ void __bad_atomic_size(void);
  * strex/ldrex monitor on some implementations. The reason we can use it for
  * atomic_set() is the clrex or dummy strex done on every exception return.
  */
-static inline int atomic_read(atomic_t *v)
+static inline int atomic_read(const atomic_t *v)
 {
     return *(volatile int *)&v->counter;
 }
diff --git a/xen/include/asm-x86/atomic.h b/xen/include/asm-x86/atomic.h
index 9bf4bc1..a16f0f6 100644
--- a/xen/include/asm-x86/atomic.h
+++ b/xen/include/asm-x86/atomic.h
@@ -86,7 +86,7 @@ void __bad_atomic_size(void);
  *
  * Atomically reads the value of @v.
  */
-static inline int atomic_read(atomic_t *v)
+static inline int atomic_read(const atomic_t *v)
 {
     return read_atomic(&v->counter);
 }
diff --git a/xen/include/xen/atomic.h b/xen/include/xen/atomic.h
index 5d5c051..6cbc6d8 100644
--- a/xen/include/xen/atomic.h
+++ b/xen/include/xen/atomic.h
@@ -37,7 +37,7 @@ typedef struct { int counter; } atomic_t;
  *
  * Atomically reads the value of @v.
  */
-static inline int atomic_read(atomic_t *v);
+static inline int atomic_read(const atomic_t *v);
 
 /**
  * _atomic_read - read atomic variable non-atomically
-- 
2.5.0


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Re: [PATCH 1/2] asm/atomic.h: common prototyping (add xen/atomic.h)

[Andrew Cooper]

On 13/07/16 12:23, Corneliu ZUZU wrote:
> Following Andrew Cooper's suggestion, create a common-side <xen/atomic.h> to
> establish, among others, prototypes of atomic functions called from common-code.
> Done to avoid introducing inconsistencies between arch-side <asm/atomic.h>
> headers when we make subtle changes to one of them.
>
> Some arm-side macros had to be turned into inline functions in the process.
>
> Also includes a minor adjustment asm-x86/atomic.h: reorder atomic_inc_and_test()
> to follow after atomic_inc().

Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>


> Signed-off-by: Corneliu ZUZU <czuzu@bitdefender.com>

Thanks for doing this!

> diff --git a/xen/include/xen/atomic.h b/xen/include/xen/atomic.h
> new file mode 100644
> index 0000000..5d5c051
> --- /dev/null
> +++ b/xen/include/xen/atomic.h
> @@ -0,0 +1,155 @@
> +/*
> + * include/xen/atomic.h
> + *
> + * Common atomic operations entities (atomic_t, function prototypes).
> + * Include _from_ arch-side <asm/atomic.h>.
> + *
> + * Copyright (c) 2016 Bitdefender S.R.L.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program; If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#ifndef __XEN_ATOMIC_H__
> +#define __XEN_ATOMIC_H__
> +
> +/*
> + * NB. I've pushed the volatile qualifier into the operations. This allows
> + * fast accessors such as _atomic_read() and _atomic_set() which don't give
> + * the compiler a fit.
> + */

I would recommend simply dropping this paragraph.  Is is very out of date.

> +typedef struct { int counter; } atomic_t;
> +
> +#define ATOMIC_INIT(i) { (i) }
> +
> +/**
> + * atomic_read - read atomic variable
> + * @v: pointer of type atomic_t
> + *
> + * Atomically reads the value of @v.
> + */
> +static inline int atomic_read(atomic_t *v);
> +
> +/**
> + * _atomic_read - read atomic variable non-atomically
> + * @v atomic_t
> + *
> + * Non-atomically reads the value of @v
> + */
> +static inline int _atomic_read(atomic_t v);
> +
> +/**
> + * atomic_set - set atomic variable
> + * @v: pointer of type atomic_t
> + * @i: required value
> + *
> + * Atomically sets the value of @v to @i.
> + */
> +static inline void atomic_set(atomic_t *v, int i);
> +
> +/**
> + * _atomic_set - set atomic variable non-atomically
> + * @v: pointer of type atomic_t
> + * @i: required value
> + *
> + * Non-atomically sets the value of @v to @i.
> + */
> +static inline void _atomic_set(atomic_t *v, int i);
> +

/**
 * atomic_cmpxchg - compare and exchange an atomic variable
 *...
 */

> +static inline int atomic_cmpxchg(atomic_t *v, int old, int new);

With those changes, Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

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Re: [PATCH 2/2] fix: make atomic_read() param const

[Andrew Cooper]

[-- Attachment #1.1: Type: text/plain, Size: 234 bytes --]

On 13/07/16 12:23, Corneliu ZUZU wrote:
> This wouldn't let me make a param of a function that used atomic_read() const.
>
> Signed-off-by: Corneliu ZUZU <czuzu@bitdefender.com>

Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

[-- Attachment #1.2: Type: text/html, Size: 787 bytes --]

[-- Attachment #2: Type: text/plain, Size: 127 bytes --]

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Re: [PATCH 1/2] asm/atomic.h: common prototyping (add xen/atomic.h)

[Julien Grall]

Hi Corneliu,

On 13/07/2016 12:23, Corneliu ZUZU wrote:
> Following Andrew Cooper's suggestion, create a common-side <xen/atomic.h> to
> establish, among others, prototypes of atomic functions called from common-code.
> Done to avoid introducing inconsistencies between arch-side <asm/atomic.h>
> headers when we make subtle changes to one of them.
>
> Some arm-side macros had to be turned into inline functions in the process.

You forgot to mention that you moved the code from 
asm-arm/arm{32,64}/atomic.h to asm-arm/arm.h.

Furthermore, this change should really be a separate patch.

>
> Also includes a minor adjustment asm-x86/atomic.h: reorder atomic_inc_and_test()
> to follow after atomic_inc().
>
> Signed-off-by: Corneliu ZUZU <czuzu@bitdefender.com>

[...]

> diff --git a/xen/include/asm-arm/atomic.h b/xen/include/asm-arm/atomic.h
> index 29ab265..8e8c5d1 100644
> --- a/xen/include/asm-arm/atomic.h
> +++ b/xen/include/asm-arm/atomic.h
> @@ -2,6 +2,7 @@
>  #define __ARCH_ARM_ATOMIC__
>
>  #include <xen/config.h>
> +#include <xen/atomic.h>
>  #include <xen/prefetch.h>
>  #include <asm/system.h>
>
> @@ -95,15 +96,6 @@ void __bad_atomic_size(void);
>      default: __bad_atomic_size(); break;                                \
>      }                                                                   \
>  })
> -
> -/*
> - * NB. I've pushed the volatile qualifier into the operations. This allows
> - * fast accessors such as _atomic_read() and _atomic_set() which don't give
> - * the compiler a fit.
> - */
> -typedef struct { int counter; } atomic_t;
> -
> -#define ATOMIC_INIT(i) { (i) }
>
>  /*
>   * On ARM, ordinary assignment (str instruction) doesn't clear the local
> @@ -138,6 +130,85 @@ static inline void _atomic_set(atomic_t *v, int i)
>  # error "unknown ARM variant"
>  #endif
>
> +#define atomic_inc_return(v)    (atomic_add_return(1, v))
> +#define atomic_dec_return(v)    (atomic_sub_return(1, v))
> +
> +/**
> + * atomic_sub_and_test - subtract value from variable and test result
> + * @i: integer value to subtract
> + * @v: pointer of type atomic_t
> + *
> + * Atomically subtracts @i from @v and returns
> + * true if the result is zero, or false for all
> + * other cases.
> + */
> +static inline int atomic_sub_and_test(int i, atomic_t *v)
> +{
> +    return 0 == atomic_sub_return(i, v);
> +}

Please don't use yoda condition. It's less readable and compiler have 
safety nowadays to prevent using "=".

> +
> +/**
> + * atomic_inc - increment atomic variable
> + * @v: pointer of type atomic_t
> + *
> + * Atomically increments @v by 1.
> + */
> +static inline void atomic_inc(atomic_t *v)
> +{
> +    atomic_add(1, v);
> +}

Regards,


-- 
Julien Grall

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Re: [PATCH 1/2] asm/atomic.h: common prototyping (add xen/atomic.h)

[Corneliu ZUZU]

On 7/13/2016 3:12 PM, Andrew Cooper wrote:
> On 13/07/16 12:23, Corneliu ZUZU wrote:
>> Following Andrew Cooper's suggestion, create a common-side <xen/atomic.h> to
>> establish, among others, prototypes of atomic functions called from common-code.
>> Done to avoid introducing inconsistencies between arch-side <asm/atomic.h>
>> headers when we make subtle changes to one of them.
>>
>> Some arm-side macros had to be turned into inline functions in the process.
>>
>> Also includes a minor adjustment asm-x86/atomic.h: reorder atomic_inc_and_test()
>> to follow after atomic_inc().
> Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>

Nice, didn't know that.

>
>
>> Signed-off-by: Corneliu ZUZU <czuzu@bitdefender.com>
> Thanks for doing this!
>
>> diff --git a/xen/include/xen/atomic.h b/xen/include/xen/atomic.h
>> new file mode 100644
>> index 0000000..5d5c051
>> --- /dev/null
>> +++ b/xen/include/xen/atomic.h
>> @@ -0,0 +1,155 @@
>> +/*
>> + * include/xen/atomic.h
>> + *
>> + * Common atomic operations entities (atomic_t, function prototypes).
>> + * Include _from_ arch-side <asm/atomic.h>.
>> + *
>> + * Copyright (c) 2016 Bitdefender S.R.L.
>> + *
>> + * This program is free software; you can redistribute it and/or modify it
>> + * under the terms and conditions of the GNU General Public License,
>> + * version 2, as published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope it will be useful, but WITHOUT
>> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
>> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
>> + * more details.
>> + *
>> + * You should have received a copy of the GNU General Public License along with
>> + * this program; If not, see <http://www.gnu.org/licenses/>.
>> + */
>> +
>> +#ifndef __XEN_ATOMIC_H__
>> +#define __XEN_ATOMIC_H__
>> +
>> +/*
>> + * NB. I've pushed the volatile qualifier into the operations. This allows
>> + * fast accessors such as _atomic_read() and _atomic_set() which don't give
>> + * the compiler a fit.
>> + */
> I would recommend simply dropping this paragraph.  Is is very out of date.

Ack.

>
>> +typedef struct { int counter; } atomic_t;
>> +
>> +#define ATOMIC_INIT(i) { (i) }
>> +
>> +/**
>> + * atomic_read - read atomic variable
>> + * @v: pointer of type atomic_t
>> + *
>> + * Atomically reads the value of @v.
>> + */
>> +static inline int atomic_read(atomic_t *v);
>> +
>> +/**
>> + * _atomic_read - read atomic variable non-atomically
>> + * @v atomic_t
>> + *
>> + * Non-atomically reads the value of @v
>> + */
>> +static inline int _atomic_read(atomic_t v);
>> +
>> +/**
>> + * atomic_set - set atomic variable
>> + * @v: pointer of type atomic_t
>> + * @i: required value
>> + *
>> + * Atomically sets the value of @v to @i.
>> + */
>> +static inline void atomic_set(atomic_t *v, int i);
>> +
>> +/**
>> + * _atomic_set - set atomic variable non-atomically
>> + * @v: pointer of type atomic_t
>> + * @i: required value
>> + *
>> + * Non-atomically sets the value of @v to @i.
>> + */
>> +static inline void _atomic_set(atomic_t *v, int i);
>> +
> /**
>   * atomic_cmpxchg - compare and exchange an atomic variable
>   *...
>   */

Ack.

>
>> +static inline int atomic_cmpxchg(atomic_t *v, int old, int new);
> With those changes, Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

Thanks too for the prompt review,
Zuzu C.

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Re: [PATCH 1/2] asm/atomic.h: common prototyping (add xen/atomic.h)

[Corneliu ZUZU]

Hi Julien,

On 7/13/2016 3:14 PM, Julien Grall wrote:
> Hi Corneliu,
>
> On 13/07/2016 12:23, Corneliu ZUZU wrote:
>> Following Andrew Cooper's suggestion, create a common-side 
>> <xen/atomic.h> to
>> establish, among others, prototypes of atomic functions called from 
>> common-code.
>> Done to avoid introducing inconsistencies between arch-side 
>> <asm/atomic.h>
>> headers when we make subtle changes to one of them.
>>
>> Some arm-side macros had to be turned into inline functions in the 
>> process.
>
> You forgot to mention that you moved the code from 
> asm-arm/arm{32,64}/atomic.h to asm-arm/arm.h.
>
> Furthermore, this change should really be a separate patch.

Noted, will do.

>
>>
>> Also includes a minor adjustment asm-x86/atomic.h: reorder 
>> atomic_inc_and_test()
>> to follow after atomic_inc().
>>
>> Signed-off-by: Corneliu ZUZU <czuzu@bitdefender.com>
>
> [...]
>
>> diff --git a/xen/include/asm-arm/atomic.h b/xen/include/asm-arm/atomic.h
>> index 29ab265..8e8c5d1 100644
>> --- a/xen/include/asm-arm/atomic.h
>> +++ b/xen/include/asm-arm/atomic.h
>> @@ -2,6 +2,7 @@
>>  #define __ARCH_ARM_ATOMIC__
>>
>>  #include <xen/config.h>
>> +#include <xen/atomic.h>
>>  #include <xen/prefetch.h>
>>  #include <asm/system.h>
>>
>> @@ -95,15 +96,6 @@ void __bad_atomic_size(void);
>>      default: __bad_atomic_size(); 
>> break;                                \
>> } \
>>  })
>> -
>> -/*
>> - * NB. I've pushed the volatile qualifier into the operations. This 
>> allows
>> - * fast accessors such as _atomic_read() and _atomic_set() which 
>> don't give
>> - * the compiler a fit.
>> - */
>> -typedef struct { int counter; } atomic_t;
>> -
>> -#define ATOMIC_INIT(i) { (i) }
>>
>>  /*
>>   * On ARM, ordinary assignment (str instruction) doesn't clear the 
>> local
>> @@ -138,6 +130,85 @@ static inline void _atomic_set(atomic_t *v, int i)
>>  # error "unknown ARM variant"
>>  #endif
>>
>> +#define atomic_inc_return(v)    (atomic_add_return(1, v))
>> +#define atomic_dec_return(v)    (atomic_sub_return(1, v))
>> +
>> +/**
>> + * atomic_sub_and_test - subtract value from variable and test result
>> + * @i: integer value to subtract
>> + * @v: pointer of type atomic_t
>> + *
>> + * Atomically subtracts @i from @v and returns
>> + * true if the result is zero, or false for all
>> + * other cases.
>> + */
>> +static inline int atomic_sub_and_test(int i, atomic_t *v)
>> +{
>> +    return 0 == atomic_sub_return(i, v);
>> +}
>
> Please don't use yoda condition. It's less readable and compiler have 
> safety nowadays to prevent using "=".

Oh yeah, given that Xen's compiled with -Wall -Werror that's not 
necessary. Ack.

>
>> +
>> +/**
>> + * atomic_inc - increment atomic variable
>> + * @v: pointer of type atomic_t
>> + *
>> + * Atomically increments @v by 1.
>> + */
>> +static inline void atomic_inc(atomic_t *v)
>> +{
>> +    atomic_add(1, v);
>> +}
>
> Regards,

Thanks,
Corneliu.

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Re: [PATCH 1/2] asm/atomic.h: common prototyping (add xen/atomic.h)

[Corneliu ZUZU]

On 7/13/2016 3:12 PM, Andrew Cooper wrote:
> On 13/07/16 12:23, Corneliu ZUZU wrote:
>> +typedef struct { int counter; } atomic_t;
>> +
>> +#define ATOMIC_INIT(i) { (i) }
>> +
>> +/**
>> + * atomic_read - read atomic variable
>> + * @v: pointer of type atomic_t
>> + *
>> + * Atomically reads the value of @v.
>> + */
>> +static inline int atomic_read(atomic_t *v);
>> +
>> +/**
>> + * _atomic_read - read atomic variable non-atomically
>> + * @v atomic_t
>> + *
>> + * Non-atomically reads the value of @v
>> + */
>> +static inline int _atomic_read(atomic_t v);
>> +
>> +/**
>> + * atomic_set - set atomic variable
>> + * @v: pointer of type atomic_t
>> + * @i: required value
>> + *
>> + * Atomically sets the value of @v to @i.
>> + */
>> +static inline void atomic_set(atomic_t *v, int i);
>> +
>> +/**
>> + * _atomic_set - set atomic variable non-atomically
>> + * @v: pointer of type atomic_t
>> + * @i: required value
>> + *
>> + * Non-atomically sets the value of @v to @i.
>> + */
>> +static inline void _atomic_set(atomic_t *v, int i);
>> +
>

Is it ok if I also omit repeating the comments which are already @ 
xen/atomic.h from the arch-side asm/atomic.h ?

Thanks,
Zuzu C.

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Re: [PATCH 1/2] asm/atomic.h: common prototyping (add xen/atomic.h)

[Andrew Cooper]

On 13/07/16 14:20, Corneliu ZUZU wrote:
> On 7/13/2016 3:12 PM, Andrew Cooper wrote:
>> On 13/07/16 12:23, Corneliu ZUZU wrote:
>>> +typedef struct { int counter; } atomic_t;
>>> +
>>> +#define ATOMIC_INIT(i) { (i) }
>>> +
>>> +/**
>>> + * atomic_read - read atomic variable
>>> + * @v: pointer of type atomic_t
>>> + *
>>> + * Atomically reads the value of @v.
>>> + */
>>> +static inline int atomic_read(atomic_t *v);
>>> +
>>> +/**
>>> + * _atomic_read - read atomic variable non-atomically
>>> + * @v atomic_t
>>> + *
>>> + * Non-atomically reads the value of @v
>>> + */
>>> +static inline int _atomic_read(atomic_t v);
>>> +
>>> +/**
>>> + * atomic_set - set atomic variable
>>> + * @v: pointer of type atomic_t
>>> + * @i: required value
>>> + *
>>> + * Atomically sets the value of @v to @i.
>>> + */
>>> +static inline void atomic_set(atomic_t *v, int i);
>>> +
>>> +/**
>>> + * _atomic_set - set atomic variable non-atomically
>>> + * @v: pointer of type atomic_t
>>> + * @i: required value
>>> + *
>>> + * Non-atomically sets the value of @v to @i.
>>> + */
>>> +static inline void _atomic_set(atomic_t *v, int i);
>>> +
>>
>
> Is it ok if I also omit repeating the comments which are already @
> xen/atomic.h from the arch-side asm/atomic.h ?

Yes - that should be fine.  No point having identical comments twice.

~Andrew

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